1. Field of the Invention
The present invention relates to improvements in an enclosed-configuration electrically powered compressor which compresses a gaseous working fluid such as a refrigerant, for use in such applications as air conditioners, and in particular vehicle air conditioners, or refrigerators etc.
2. Description of Prior Art
A prior art type of electrically powered compressor for use in cooling applications is described for example in Japanese patent 6-74787. This compressor is of cylindrical configuration, positioned with a vertical orientation, and having an internal space which encloses an electric motor and a compressor section arranged in series. The electric motor is disposed with the drive shaft oriented vertically, within a lower part of the casing, and drives the compressor section (which is a scroll-configuration compressor) that is located within an upper part of the casing. The drive shaft of the electric motor drives an eccentric shaft of the compressor section via a bearing, whereby a moveable scroll member is driven with respect to a fixed scroll member.
The respective locations of the electric motor and the compressor section within a lower part and an upper part of the casing, respectively, serve to ensure that damage does not occur as a result of a mixture of refrigerant and lubricating oil being drawn into the compressor section. Most of the lubricating oil remains in an oil pool in a lower part of the region which contains the electric motor. The lubricating oil is drawn up from the oil pool through lubricating oil through-holes formed in the axis of the rotor of the electric motor, to be thereby supplied to various parts of the apparatus.
The stator coil is a continuously-wound type of coil (i.e., as opposed to a segment type of coil, described hereinafter) formed on the stator core, as shown in the cross-sectional view of FIG. 1 of that patent disclosure.
A refrigerant intake aperture which opens into the internal space in the casing is located facing an intake aperture of the compressor section, so that most of the refrigerant which flows through the refrigerant intake aperture is directly drawn into the compressor section. As a result, that flow of refrigerant does not effect any substantial cooling of the stator coil, and in particular of the outer end portions of the stator coil.
Thus with such a type of prior art electrically powered compressor, little consideration is given to cooling of the electric motor. In order to prevent motor overheating, it is necessary to use an electric motor having a power rating which is sufficiently large to ensure that sufficient dissipation of heat will occur, rather than a motor whose power output capability is optimum with respect to the requirements for driving the compressor section. In addition, when such a continuously-wound type of stator coil is used, the occupancy factor of the stator slots (i.e., percentage of cross-sectional area of a slot that is occupied by conductors) is relatively low, by comparison for example with a segment-configuration coil. As result, it is difficult to make the stator of such an electric motor small in diameter. In addition, the conductors in the coil end portions of the stator coil may be sharply bent outward, and thus may readily be damaged, or the insulation thereon may be damaged. For these reasons, the coil end portions can only be made of limited length.
For the above reasons, with a prior art type of electrically powered compressor, it has been difficult to achieve both a high level of drive power combined with small size and light weight for the electric motor. Hence, it has not been possible to achieve an electrically powered compressor which has high efficiency and is also compact and light in weight.